Bt棉田边缘杂草带对棉田内叶螨发生的影响

2003～2004年,在冀南棉区系统研究了棉田边缘杂草带对棉田内叶螨发生的影响。试验设3个处理：转Bt基因棉化防田(使用杀螨剂控制棉叶螨且保留棉田边缘杂草)、转Bt基因棉对照田(保留棉田边缘杂草)和转Bt基因棉除草田(去除棉田边缘杂草)。结果表明,2003年6月28日～8月7日,处理间的叶螨发生量和有螨株率差异明显。2003年叶螨发生高峰期(7月28日),对照田的百株平均螨量达834头,分别是化防田、除草田的9.4倍和11.5倍;对照田的有螨株率的峰值为34.7%,分别高于化防田和除草田6.4%和12%;棉叶螨的总计值,对照田分别是化防田和除草田的5.8倍和5.5倍。2004年7月10日～8月29日,对照田的百株螨量和有螨株率明显高于除草田和化防田。2004年叶螨发生高峰期（8月10日）,对照田的百株平均螨量达1 222头,分别是化防田、除草田的4.3倍和23.4倍;对照田的有螨株率的峰值达100%,分别比除草田和化防田多75%和87%;棉叶螨的总计值,对照田分别是化防田和除草田的4.9和9.7倍。两年中,除草田和化防田的百株螨量和有螨株率峰值出现日期有所不同。对照田内,棉田边缘杂草至所调查的棉株距离同螨害指数呈显著(P＜0.05)或极显著(P＜0.01)的负相关。本研究表明,去除棉田边缘杂草的棉田,叶螨发生始期较晚且发生量较少;棉田边缘杂草到取样点的距离与棉叶螨的为害程度呈直线负相关,距离越近,叶螨的发生为害越重。     

Comparative incidence of cotton spider mites on transgenic Bt versus conventional cotton in relation to contents of secondary metabolites

With the wide adoption of transgenic Bacillus thuringiensis (Bt) cotton, the incidence of bollworm has reduced significantly, but secondary pests such as cotton spider mites have become serious problems in Bt cotton fields. The objective of the present study was to investigate the underlying mechanism of increased incidence of secondary pests in Bt cotton. Two transgenic cotton varieties, sGK321 and Bt-C12, and their non-transformed counterparts, SY321 and C12, were used to study differences in the incidence of spider mites in relation to secondary metabolites. Plants of each cotton cultivar were infested with five female adult spider mites and then isolated. Leaf samples with a pair of adult mites of the same age were transferred individually into Petri dishes for examination of egg laying and duration of development stages. The number of spider mites on Bt-C12 and sGK321 was more than that on C12 and SY321. The cotton spider mites feeding on Bt-C12 laid significantly more eggs than those feeding on C12; those feeding on sGK321 laid significantly more eggs than those feeding on SY321. The generation time of spider mites feeding on Bt-C12 was greatly reduced relative to those feeding on C12. Also, the generation time of mites feeding on sGK321 was shorter than those feeding on SY321. Gossypol and tannin contents in leaves of Bt-C12 were substantially lower than those in C12, and the contents in leaves of sGK321 were significantly lower than those in leaves of SY321. The occurrence of spider mites was more serious on Bt than non-Bt cotton, and the fitness of the mites on Bt cotton was higher than on non-Bt cotton. Reductions in gossypol and tannin contents in Bt cotton decreased the generation time and increased the number of eggs of cotton spider mites.     

Transfer of Cry1Ac and Cry2Ab proteins from genetically engineered Bt cotton to herbivores and predators

With the cultivation of Bt cotton, the produced insecticidal Cry proteins are ingested by herbivores and potentially transferred along the food chain to natural enemies, such as predators. In laboratory experiments with Bollgard II cotton, concentrations of Cry1Ac and Cry2Ab were measured in Lepidoptera larvae (Spodoptera littoralis, Heliothis virescens), plant bugs (Euschistus heros), aphids (Aphis gossypii), whiteflies (Bemisia tabaci), thrips (Thrips tabaci, Frankliniella occidentalis), and spider mites (Tetranychus urticae). Tritrophic experiments were conducted with caterpillars of S. littoralis as prey and larvae of ladybird beetles (Harmonia axyridis, Adalia bipunctata) and lacewings (Chrysoperla carnea) as predators. Immunological measurements (ELISA) indicated that herbivores feeding on Bt cotton contained 5%–50% of the Bt protein concentrations in leaves except whiteflies and aphids, which contained no or only traces of Bt protein, and spider mites, which contained 7 times more Cry1Ac than leaves. Similarly, predators contained 1%–30% of the Cry protein concentration in prey. For the nontarget risk assessment, this indicates that Bt protein concentrations decrease considerably from one trophic level to the next in the food web, except for spider mites that contain Bt protein concentrations higher than those measured in the leaves. Exposure of phloem sucking hemipterans is negligible.     

Attraction of Phytoseiulus persimilis (Acari: Phytoseiidae) towards volatiles from various Tetranychus urticae-infested plant species

Plants infested with the spider mite Tetranychus urticae Koch, may indirectly defend themselves by releasing volatiles that attract the predatory mite Phytoseiulus persimilis Athias-Henriot. Several plants from different plant families that varied in the level of spider mite acceptance were tested in an olfactometer. The predatory mites were significantly attracted to the spider mite-infested leaves of all test plant species. No differences in attractiveness of the infested plant leaves were found for predatory mites reared on spider mites on the different test plants or on lima bean. Thus, experience with the spider mite-induced plant volatiles did not affect the predatory mites. Jasmonic acid was applied to ginkgo leaves to induce a mimic of a spider mite-induced volatile blend, because the spider mites did not survive when incubated on ginkgo. The volatile blend induced in ginkgo by jasmonic acid was slightly attractive to predatory mites. Plants with a high degree of direct defence were thought to invest less in indirect defence than plants with a low degree of direct defence. However, plants that had a strong direct defence such as ginkgo and sweet pepper, did emit induced volatiles that attracted the predatory mite. This indicates that a combination of direct and indirect defence is to some extent compatible in plant species.     

取食转基因抗虫棉上的棉蚜对粉舞蛛存活和发育的影响

本文以转双价基因棉花SGK321、棉蚜Aphis gossypii和粉舞蛛Alopecosa pulverulenta为对象,研究了捕食转基因植物上的植食性害虫对多食性捕食性天敌的影响。结果表明,粉舞蛛可以猎食棉蚜,但单独捕食棉蚜不足以长期维持若蛛的生存和发育; 与果蝇混合饲养,能显著提高若蛛存活率和体重。在猎物过量或数量不足的情况下,单独捕食转基因棉或常规棉上的棉蚜,若蛛的生存曲线和体重差异不显著。在猎物过量的条件下,用转基因棉上的棉蚜与果蝇混合饲养,若蛛的存活率显著高于用常规棉上的棉蚜与果蝇混合的处理; 但这两种处理下,若蛛的体重差异不显著。在猎物数量不足的情况下,用转基因棉或常规棉上的棉蚜与果蝇混合饲养,若蛛的存活率和体重差异都不显著。可见,转双价基因棉花SGK321上的棉蚜对粉舞蛛的存活和发育没有显著的不利影响。     

Positive association between thrips and spider mites in seedling cotton

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Changes in photosynthetic and transpiration rates of cotton leaves infested with the cotton aphid, Aphis gossypii: Unrestricted infestation

The influence of aphid, Aphis gossypii, feeding on photosynthesis and transpiration in cotton plants was investigated under greenhouse conditions. Four population densities of 0, 5, 10, and 25 aphids were used to infest individual cotton leaves. Gas exchange rates were determined for single attached cotton leaves after 9, 18, and 27 days of aphid infestation. Aphid feeding changed photosynthetic rates and transpiration rates. These changes were proportional to the number of aphids and the length of infestation period. Photosynthetic rates were significantly reduced in infested leaves with 25 aphids over 18 days, whereas significant reduction in photosynthetic rates was recorded within 27 days in infested leaves with 5, 10, and 25 aphids in comparison to their respective control. Initial population of 10 aphids increased significantly the transpiration rate of infested leaves over 9 and 27 days. Leaves of plants with 25 aphids had significantly greater transpiration rate than the control at all times.     

Prey-mediated effects of mCry51Aa2-producing cotton on the predatory nontarget bug Orius majusculus (Reuter)

Genetically engineered (GE) cotton, MON 88702, is protected against certain sucking pests, such as plant bugs and thrips, by producing mCry51Aa2, a modified protein from Bacillus thuringiensis (Bt). Predatory pirate bugs (Orius spp.), natural enemies contributing to biological pest control, are also sensitive to the insecticidal protein when exposed continuously to high concentrations. We evaluated effects of MON 88702 on Orius majusculus when fed prey types with different mCry51Aa2 concentrations. When neonates were provided exclusively Tetranychus urticae spider mites reared on MON 88702 (high mCry51Aa2 content), adverse effects on predator survival and development were confirmed, compared with specimens fed prey from near-isogenic non-Bt cotton. When fed a mixture of T. urticae and Ephestia kuehniella eggs (mCry51Aa2-free), predator life table parameters were similar to the treatment where eggs were fed exclusively. When mCry51Aa2-containing spider mites were provided for a limited time at the beginning or the end of juvenile development, effects were less pronounced. While pirate bug nymphs showed similar consumption rates for prey from Bt and non-Bt cotton, choice experiments revealed a preference for E. kuehniella eggs over spider mites. Lepidopteran larvae (Spodoptera littoralis, high mCry51Aa2 content) or cotton aphids (Aphis gossypii, mCry51Aa2-free) reared on MON 88702 as alternative prey did not result in adverse effects on O. majusculus. Our study suggests limited risk of mCry51Aa2-producing cotton for O. majusculus, because its sensitivity for the Bt protein is relatively low and its natural food consists of diverse prey species with varying concentrations of Bt protein.     

棉花型和瓜型棉蚜形态和生态适应力的分化

棉蚜由于长期在同种或同类植物上生活,形成了多种寄主专化型。本研究以室内长期用单一寄主培养的棉花型和瓜型棉蚜为材料,采用形态测定、生命表技术、对寄主的选择性试验,以及接触刺激等方法,研究了两寄主型棉蚜的形态分化和生态适应力的差异。结果表明,瓜型棉蚜的一些形态特征值（如体长）极显著地大于棉花型个体,但是头宽、口针和各腿节的长度与体长的比值却极显著的小于棉花型个体。采用7个形态指标与体长的比值,可将瓜型和棉花型棉蚜区分开来。在24℃和26℃下瓜型蚜的净增殖率（R₀）极显著地高于棉花型蚜。27℃和32℃显著缩短了瓜型蚜的平均世代长度,而对棉花型蚜无影响。棉花型蚜对接触刺激的反应比瓜型蚜敏感。两寄主型蚜对寄主的选择能力表现为瓜型蚜显著强于棉花型蚜。因此,两寄主型棉蚜存在明显的形态和生态适应力的分化。     

Local and systemic effects of two herbivores with different feeding mechanisms on primary metabolism of cotton leaves

Caterpillars and spider mites are herbivores with different feeding mechanisms. Spider mites feed on the cell content via stylets, while caterpillars, as chewing herbivores, remove larger amounts of photosynthetically active tissue. We investigated local and systemic effects of short-term caterpillar and spider mite herbivory on cotton in terms of primary metabolism and growth processes. After short-term caterpillar feeding, leaf growth and water content were decreased in damaged leaves. The glutamate/glutamine ratio increased and other free amino acids were also affected. In contrast, mild spider mite infestation did not affect leaf growth or amino acid composition, but led to an increase in total nitrogen and sucrose concentrations. Both herbivores induced locally increased dark respiration, suggesting an increased mobilization of storage compounds potentially available for synthesis of defensive substances, but did not affect assimilation and transpiration. Systemically induced leaves were not significantly affected by the treatments performed in this study. The results show that cotton plants do not compensate the loss of photosynthetic tissue with higher photosynthetic efficiency of the remaining tissue. However, early plant responses to different herbivores leave their signature in primary metabolism, affecting leaf growth. Changes in amino acid concentrations, total nitrogen and sucrose content may affect subsequent herbivore performance.     

Impact of transgenic Bacillus thuringiensis cotton on a non-target pest Tetranychus spp. in northern China

Field studies were carried out to evaluate the effect of two transgenic cotton varieties (SGK321 carrying Cry1A+CpTI and DP99B carrying Cry1Ac) and the conventional variety (shiyuan321‐parental line of SGK321) on spider mites, Tetranychus spp. from 2002 to 2004. In 2002, this experiment included three treatments: Bt cotton field (SGK321) treated with acaricides against spider mites, untreated non‐Bt cotton field (Shiyuan321), and untreated Bt cotton field (SGK321). In 2003–2004, there are four types of treatments after a new transgenic Bt cotton variety, DP99B (non‐chemical control), was added into the experiments. The results showed that there were no significant difference in densities of spider mites among Bt without acaricides and non‐Bt without acaricides cotton fields, nor was there a significant difference in damage of spider mites to cotton among these treatments (P > 0.1). However, there are significant differences (P < 0.05) in densities of spider mites and damage caused by spider mites between cotton fields with and without acaricides. Acaricide significantly reduced the densities of spider mites in Bt cotton (P < 0.05). These results suggest that Bt cotton has no effect on spider mites populations. However, spider mites have the potential for severe damage in Bt cotton fields. Acaricides are essential tools in controlling cotton spider mites in northern China.     

Remotely sensing arthropod and nutrient stressed plants: a case study with nitrogen and cotton aphid (Hemiptera: Aphididae)

Remote sensing can be used in combination with ground sampling to detect aphid- (Aphis gossypii Glover) infested cotton (Gossypium hirsutum L.). Changes in wavelengths in the near-infrared (NIR) have proven useful for such detection, but these changes can be confused with other factors stressing plants, such as water deficiency and nutrient status. This study was designed to test the utility of this technology to distinguish between two factors stressing plants: nitrogen deficiency and aphids. Field plots were created by applying varying rates of nitrogen to cotton at different dates in the growing season in 2003 and 2004. Subplots were created by applying disruptive insecticides, which increased aphid populations in a portion of the subplots. Airplane and satellite remote sensing data in 2003 and 2004 were supplemented with ground sampling of aphid populations in both years. Insecticide application, nitrogen application rate and date influenced aphid abundance. Cotton with higher aphid populations could be distinguished from cotton with natural aphid infestations independent of plant nitrogen status using a NIR wavelength in 2003 and a proprietary 2004 index. Complex distinctions among varying nitrogen treatments and aphid abundance were not possible using this data. In the future, possible confounding factors should be investigated from the perspective of their change on crop physiology before remote sensing can be used in an integrated pest management (IPM) program.     

土耳其斯坦叶螨为害棉叶的生理变化及光谱特征分析

对土耳其斯坦叶螨Tetranychusturkestani(VgarovetNikolski)为害程度不同(0,1,2,3,4级)的棉叶进行光谱测试,并按螨害级数测定光谱测试后棉叶的叶绿素和类胡萝卜素含量。结果表明随着螨害的逐渐加重,棉叶的叶绿素含量逐渐下降,类胡萝卜素含量逐渐上升。光谱测试结果在可见光区,绿峰两侧波段的光谱反射率随螨害加重逐渐增大,差异明显;在近红外区,748~863nm波段的光谱反射率随螨害加重逐渐减小,差异极显著。同时,利用一阶微分求取不同螨害级数棉叶的红边并计算红边参数,通过分析发现,棉花受叶螨危害后单叶光谱的红边发生明显的蓝移现象,红边振幅、红边振幅与最小振幅的比值以及红边峰值面积的值随着螨害加重逐渐减小,结果认为红边能很好地反映棉叶受棉叶螨危害的程度。     

Aesthetic damage thresholds for twospotted spider mites (Acari: Tetranychidae) on impatiens: effect of plant age and level of infestation

The effects of plant age and infestation level of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), on visible plant damage, and the effect of plant age on spider mite population growth on impatiens, Impatiens wallerana Hook.f. (Ericales: Balsaminaceae), were determined by inoculating impatiens plants of three different ages with two densities of spider mites. Each plant was inoculated with either one adult female mite per three leaves or six leaves based on the average number of leaves on plants of each of the three age classes. Subsequently, leaf damage was correlated with mite-days (cumulative spider mite density) per leaf. The results showed that older aged plants exhibited greater damage than younger plants. Regression models of damage thresholds for each plant age suggest that monitoring for spider mites must be done periodically throughout the entire plant production cycle, but that more attention should be given toward the end of the cycle. Measurements of visible leaf damage were correlated with plant marketability. Specifically, the level of damage (proportion of damaged leaves per plant) at which plant marketability changes from a "premium" to a "discounted" category was 0.04-0.06. Thus, regression equations of the damage threshold could be used to estimate a cumulative spider mite density or mite-days equivalent to the economic threshold. Based on these equations, 5% leaf damage corresponds to 2.1, 1.51, and 1.25 mite-days for youngest, intermediate, and oldest plants, respectively. Because the damage threshold on impatiens was shown to be very low, the action threshold for biological control is essentially zero, and predators would need to be released as soon as damage is observed.     

棉蚜饲养技术——笼罩法

在长期的试虫饲养过程中 ,摸索出一种新的棉蚜饲养方法———笼罩法。利用A4幅面的透明胶片和纱网制成笼罩。并于室内催芽 ,培育棉花种苗 ,可利用自制笼罩于光照培养箱内隔离饲养棉蚜 ,经与琼脂叶片法和自制Blackmanbox方法比较 ,笼罩法具有省时省力、不受季节限制、棉蚜生长条件好以及取食活体植株等许多突出的优点。     

Within-plant distribution of cotton aphids, Aphis gossypii Glover (Hemiptera: Aphididae), in Bt and non-Bt cotton fields

Knowledge of the vertical and horizontal distribution of Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified cotton plants over time could help optimize decision-making in integrated cotton aphid management programs. Therefore, the aim of the present study was to determine the vertical and horizontal distribution of A. gossypii in non-transgenic Bt cotton and transgenic Bt-cotton over time during two cotton seasons by examining plants throughout the seasons. There was no significant interaction between years and cotton cultivar treatments for apterous or alate aphids. Considering year-to-year data, analyses on season-long averages of apterous or alate aphids showed that aphid densities per plant did not differ among years. The number of apterous aphids found per plant for the Bt transgenic cultivar (2427 apterous aphids per plant) was lower than for its isoline (3335 apterous aphids per plant). The number of alate aphids found per plant on the Bt transgenic cultivar (12.28 alate aphids per plant) was lower than for the isoline (140.56 alate aphids per plant). With regard to the vertical distribution of apterous aphids or alate aphids, there were interactions between cotton cultivar, plant age and plant region. We conclude that in comparison to non-Bt cotton (DP 4049), Bt cotton (DP 404 BG (Bollgard)) has significant effects on the vertical, horizontal, spatial and temporal distribution patterns of A. gossypii, showing changes in its distribution behaviour inside the plant as the cotton crop develops. The results of our study are relevant for understanding the vertical and horizontal distribution of A. gossypii on Bt cotton cultivar (DP 404 BG (Bollgard)) and on its isoline (DP 4049), and could be useful in decision-making, implementing controls and determining the timing of population peaks of this insect.     

转基因杨树林下种植转基因棉花对转基因杨棉复合系统内节肢动物群落多样性的影响

【目的】转Bt基因棉花和转Bt基因杨树在我国已推广使用。本研究的目的是调查和分析不同转基因杨棉复合系统内地上节肢动物群落多样性变化,为转基因杨树大规模应用提供生态安全方面的数据。【方法】2019年4-10月,在河北任丘采取欧洲黑杨Populus nigra林下种植转基因棉花Gossypium hirsutum的模式,设置转基因杨树 转基因棉花(复合生态系统1)和非转基因杨树-转基因棉花(复合生态系统2)两种杨棉复合系统,调查杨树和棉花地上部植株节肢动物种类和个体数量,比较节肢动物各功能群的物种数量和个体数量以及香农指数、优势集中性指数、均匀度指数等群落多样性指数,并测定了转基因杨树和棉花叶片Bt蛋白含量。【结果】复合生态系统1中转基因杨树和棉花各自植株上鳞翅目种群累计个体数均显著低于复合生态系统2相应植株上的个体数量。转基因杨树上叶甲类累计个体数量显著高于非转基因杨树上的,寄生蜂类累计个体数量则显著低于非转基因杨树上的。在6月5日、6月21日和9月7日的调查中,转基因杨树上的节肢动物群落香农指数显著高于非转基因杨树上的。除鳞翅目害虫外,2个复合系统中棉株上节肢动物各功能群累计个体数量无显著性差异,香农指数、优势集中性指数和均匀度指数随时间变化的趋势基本一致且同一调查时间无显著性差异,仅在8月17调查中复合生态系统1中棉株上节肢动物香农指数显著高于复合生态系统2棉株上的。将杨树和棉花上节肢动物各类群累计数量相加作为系统整体,复合生态系统1和复合生态系统2在香农指数、优势集中性指数和均匀度指数数值上无显著差异。在调查后期,2个复合系统中节肢动物种群均向杨树叶片聚集。转基因棉花叶片Bt蛋白含量在各调查期均显著高于转基因杨树叶片的。【结论】转基因杨树对靶标害虫种群数量有较好的控制作用,对同系统内棉花上鳞翅目害虫数量亦有协同控制作用。转基因杨棉复合系统中地上节肢动物群落结构稳定,对系统内棉花地上部节肢动物群落多样性无显著影响。靶标害虫对转Bt基因杨树的抗性发展需持续监测。     

为害罂粟的两种主要害虫的生物学习性初步观察

罂粟(PapaversomniferumL .)是重要的药用植物之一,其中的鸦片及其衍生物主要在医药工业中用于合成麻醉止痛药、安眠药和镇定药物。作者对罂粟上发生的2种主要虫害,即甘蓝夜蛾BarathrabrassicaeL .和山楂叶螨TetranychusviennensisZacher的发生规律进行了调查。结果表明,甘蓝夜蛾幼虫有群集性,主要取食罂粟叶片,食尽叶肉后进入蒴果取食种子,是罂粟的毁灭性虫害,山楂叶螨主要危害多年生罂粟,尤其在高温干燥季节危害严重。     

Influence of dispersal from almonds on the population dynamics and acaricide resistance frequencies of spider mites infesting neighboring cotton

Neighboring almond and cotton fields were sampled for spider mites in four locations in the San Joaquin Valley of California. The dominant species in the almonds wasTetranychus pacificus McGregor. In three cotton sites.T. pacificus was present in significantly higher densities near the almonds on at least one sampling date. In contrast.T. urticae Koch andT. turkestani Ugarov & Nikolski were equally abundant across the cotton fields. Almonds appeared to act as a continuous early-season source ofT. pacificus for cotton, with peaks in aerial dispersal from almonds occurring due to overcrowding, plant water stress, and applications of repellent acaricides. Cotton, which experienced little water stress, supported very high densities of spider mites and so acted primarily as a sink for spider-mite dispersal from almonds and other field crops throughout the growth-season. The frequencies of resistance expressed byT. pacificus andT. urticae were similar between neighboring crops, even if the acaricide had been registered for use only in almonds (cyhexatin) or cotton (dicofol). Thus, longterm acaricide selection and movement of spider mites between the two crops resulted in similar proportions of resistant individuals. In these study sites, large-scale dispersal ofT. pacificus from almonds rarely directly affected acaricide efficacy in cotton, because resistance frequencies were similar for spider mites from the two crops and because acaricide applications were usually made in cotton after dispersal from almonds was completed. In two cotton sites, field selection with dicofol was reversed by subsequent immigration of spider mites from neighboring field crops.     

Within-plant distribution of twospotted spider mites (Acari: Tetranychidae) on impatiens: development of a presence-absence sampling plan

The twospotted spider mite, Tetranychus urticae Koch, is an important pest of impatiens, a floricultural crop of increasing economic importance in the United States. The large amount of foliage on individual impatiens plants, the small size of mites, and their ability to quickly build high populations make a reliable sampling method essential when developing a pest management program. In our study, we were particularly interested in using spider mite counts as a basis for releasing biological control agents. The within-plant distribution of mites was established in greenhouse experiments and these data were used to identify the sampling unit. Leaves were divided into three zones according to location on the plant: inner, intermediate, and other. On average, 40, 33, and 27% of the leaves belonged to the inner, intermediate, and other leaf zones, respectively. However, because 60% of the mites consistently were found on the intermediate leaves, intermediate leaves were chosen as the sampling unit. These results lead to the development of a presence-absence sampling method for T. urticae by using Taylor coefficients generic for this pest. The accuracy of this method was verified against an independent data set. By determining numerical or binomial sample sizes for consistently estimating twospotted spider mite populations, growers will now be able to determine the number of predatory mites that should be released to control twospotted spider mites on impatiens.